In recent years, flat panel displays have been widely used in various commodities and fields, and the flat panel displays are required to have a larger size, a higher image quality, and a lower power consumption.
Under these circumstances, an organic EL display device is attracting considerable attention as an all-solid-state flat panel display with excellent low-voltage driving capability, high-speed responsibility, and self-luminous property. The organic EL display device includes an organic EL element that utilizes the electroluminescence of an organic material.
In an active matrix type organic EL display device, e.g., a thin-film organic EL element is provided on a substrate having TFTs (thin-film transistors). The organic EL element includes an organic EL layer (including a light emitting layer) that is disposed between a pair of electrodes. The TFTs are connected to one of the pair of electrodes. A voltage is applied across the pair of electrodes so that the light emitting layer emits light, thereby displaying images.
In the above conventional organic EL display device, it is known that a sealing film is formed on the organic EL element in order to prevent the degradation of the organic EL element due to moisture or oxygen. Moreover, a laminated film composed of an inorganic layer and an organic layer is used as the sealing film of the conventional organic EL display device.
Specifically, a conventional organic EL display device including an encapsulating film has been proposed, as described in, e.g., Patent Document 1. The encapsulating film is formed so that the density and thickness of the encapsulating film increase in a direction from a center portion to an edge portion of the organic EL display device. This conventional organic EL display device can prevent the permeation of moisture or oxygen through the sides of the device.
A conventional organic EL display device including a sealing film in which each of organic layers and each of inorganic layers are alternately stacked has been proposed, as described in, e.g., Patent Document 2. In the sealing film, each of the organic layers other than the uppermost organic layer is formed in a region that is smaller than the inorganic layer. Thus, except for the uppermost organic layer that adheres to a sealing glass substrate, the ends of each of the organic layers are covered with two stacked inorganic layers so as not to be exposed to the outside. This conventional organic EL display device can prevent the deterioration of the organic layers due to exposure.